This invention relates to a single in-line type semiconductor device having external lead-in wires arranged as an alternate offset array.
As a power integrated circuit for use in audio equipment and for motor control, for instance, a single in-line (SIL) type package is employed, which has a plurality of external lead-wires extending from one side of the package. There are two types of SIL package: (1) a lead straight type having external lead-in wires in a single array, and (2) an alternately offset type having a plurality of external lead wires arranged in two rows.
FIG. 1 is a side view, partly in section, showing an external appearance of a conventional offset pin type integrated circuit. Heat sink 22 made of metal is embedded in one surface of package 21 made of, for example, an insulating resin or ceramics. A plurality of external lead-in wires 23 extend from the bottom surface of package 21, and are alternately bent in the neighborhood of their base ends, in a direction opposite to that in which heat sink 22 is located. As a result, external lead-in wires 23 are arranged in two rows.
In the process of attaching an integrated circuit to an electronic device, the external lead-in wires are soldered to a printed circuit board, and the resultant structure is fixed to the heat sink by means of, for example, a screw.
FIG. 2 is a side view showing the aforementioned integrated circuit incorporated into an electronic device. In the arrangement shown in FIG. 2, reference numeral 31 represents a printed circuit board to which integrated circuit 20 and various elements are joined by soldering. Internal heat sink 33 is mounted on the case side of the electronic device, and serves also as an IC mounting plate. External heat sink 34 is fixed by screw 35 to internal heat sink 33.
When external heat sink 34 is to be attached to internal heat sink 33 by means of the screw, integated circuit 20 cannot be located currently unless it is set upright relative to printed circuit board 31.
However, heat sink 22 made of metal is placed on one surface side of integrated circuit 20 so that, upon the attachment of external lead-in wires 23 to the printed circuit board by soldering, integrated circuit 20 is fixed in a tilted fashion, as is shown in FIG. 2, due to a heavy weight being applied to that side of the package where heat sink 22 is located. Where external lead-in wires 23 are soldered to printed circuit board 31, with integrated circuit 20 not set upright over printed circuit board 31, stress is applied to integrated circuit 20 by the insertion of the screw. As a result, cracks may occur in the semiconductor pellet of integrated circuit 20. If integrated circuit 20 is erected by applying an undue force, then there is a possibility that a breakage will occur on the interconnection layer of the printed circuit board.